CD8A and squamous cell carcinoma: However, when tracing the highly plastic state of PTMS using tumor single cells, we found that PTMS was highly expressed in tumor-infiltrating lymphocytes (TILs), particularly TILs from squamous cell carcinoma (SCC), such as Tfh, Th17, Treg, and activated and exhausted CD8+ T cells (Figures 7E–H), whereas PTMS showed relatively low expression in naïve T cells (Figures 7G, H).